The overall objective of the proposed research is to study the visual contributions to eye movement generation, with special emphasis on the smooth pursuit and optokinetic systems. We will extend our ongoing work on the role of the dorsolateral pontine nucleus in smooth pursuit to the primate pretectum and accessory optic system (AOS). We will pursue these studies by several different approaches. First, the visual and oculomotor response properties of single units in the pretectum and accessory optic nuclei of the trained monkey will be investigated. Single unit recordings will be conducted in all subdivisions of the pretectum where, in preliminary studies (Mustari and Fuchs, 1988), we found units that discharged during smooth pursuit eye movements and during optokinetic visual stimulation. Eye movements will be monitored with the scleral search coil technique. The response properties of units will be tested during smooth pursuit, optokinetic and saccadic eye movements as well as during visual and vestibular stimulation. We will use microelectrical stimulation in an attempt to elicit eye movements from different sites. Second, small reversible (xylocaine) and permanent (ibotenic acid) chemical lesions will be placed in pretectal nuclei (e.g., nucleus of the optic tract, pretectal olivary nucleus) and the AOS (e.g., lateral terminal nucleus) to assess their potential contributions to optokinetic and smooth pursuit eye movements as well as to the pupillary light reflex. Third, the afferent and efferent connections of all the pretectal nuclei (e.g., nucleus of the optic tract, posterior pretectal nucleus, pretectal olivary nucleus) and AOS nuclei will be studied using very small injections of retrograde and anterograde tracers (horseradish peroxidase, rhodamine beads and tritiated amino acids). These tracers will be placed at locations where we have first recorded and characterized unit response types. Finally, electrical stimulation will be used to antidromically activate identified pretectal unit types from different efferent targets, including the dorsal cap of the inferior olive, nucleus prepositus hypoglossi, vestibular nuclei and oculomotor complex, to reveal the functional connectivity of the pretectum with other visual and oculomotor areas. This study will advance our understanding of the visual contributions to eye movement generation by the pretectum and AOS may assist the diagnosis and treatment of smooth pursuit and optokinetic eye movement disorders.